在本实例中，首先我们利用SQLiteOpenHelper类建立一个数据库，并写好增、删、查等方法，通过SimpleCursorAdapter连接listview实现数据库的增加、查询以及长按删除的功能。
首先，我们先认识一下什么是SQLiteOpenHelper类。
Android为了操作SQlite数据库，提供了SQLiteDatabase类，其内封装了insert 、delete、update 、query 、执行SQL命令等操作。同时又为SQLiteDatabase提供了一个辅助类，SQLiteOpenHelper。它提供了两个重要的方法，分别是：
onCreate(SQLiteDatabase db)：用户初次使用软件时生成数据库，一旦数据库存在则不会调用此方法。函数是在第一次创建数据库的时候执行的，仅仅生成DataBaseHelper对（SQLiteOpenHelper类型）的时候是不会调用该函数的，而只有当调用DataBaseHelper对象的getReadableDataBase时或者是调用了getWritableDataBase时，如果是第一次创建数据库，那么就一定会调用onCreate()函数。
onUpgrade(SQLiteDatabase db，int oldVersion，int vewVersion)：用于升级软件时更新数据库表结构，如增加表、列字段等操作。
实现了这两个方法，就可以用它的getWritableDatabase()和getReadableDatabase()来获得数据库（SQLiteDatabase 对象）。
如果用户需要升级数据库表结构，需要主动调用onUpgrade(SQLiteDatabase db，int oldVersion，int vewVersion),传入一个新的版本的号。
建立一个新数据库的代码如下：
package com.example.listview_sqlite_xu;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class NewsSearchDatabaseHelper extends SQLiteOpenHelper {
final String SQL_CREATE_TABLE = "create table news_table (" +
"_id integer primary key autoincrement, " +
"news_tittle varchar(50), " +
"news_content varchar(5000))";
public NewsSearchDatabaseHelper(Context context, String name, int version) {
super(context, name, null, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(SQL_CREATE_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
System.out.println("call update");
}
}
接下来我们建立MainActivity：
package com.example.listview_sqlite_xu;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;
import android.database.SQLException;
import android.os.Bundle;
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.View;
import android.view.View.OnCreateContextMenuListener;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.Toast;
public class MainActivity extends Activity {
private NewsSearchDatabaseHelper helper; //数据库帮助类
private EditText et_tittle; //输入新闻
private EditText et_content; //输入新闻内容
private ListView listView; //显示新闻列表
ArrayList<HashMap<String, Object>> listData; // key-value
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
helper = new NewsSearchDatabaseHelper(getApplicationContext(), "news", 1); //创建一个名为“news”的数据库
//初始化控件
et_tittle = (EditText) findViewById(R.id.et_news_tittle);
et_content = (EditText) findViewById(R.id.et_news_content);
listView = (ListView) findViewById(R.id.lv_news);
listView.setOnCreateContextMenuListener(listviewLongPress);
// 设置长按事件
}
public void onClick(View view) {
int id = view.getId();
if(id==R.id.bt_add)
insertNews();
else if(id== R.id.bt_query)
queryNews();
}
private void inflateListView(Cursor cursor) {
SimpleCursorAdapter cursorAdapter = new SimpleCursorAdapter(getApplicationContext(), R.layout.item, cursor, new String[]{"news_tittle", "news_content"}, new int[]{R.id.tittle, R.id.content},1);
listView.setAdapter(cursorAdapter);
}
private void insertNews() {
String tittle = et_tittle.getText().toString();
String content = et_content.getText().toString();
helper.getReadableDatabase().execSQL("insert into news_table values(null, ?, ?)", new String[]{tittle, content});
Cursor cursor = helper.getReadableDatabase().rawQuery("select * from news_table", null);
inflateListView(cursor); //刷新listview
}
private boolean deleteNews(int _id) {
String whereClause = "_id=?";
String[] whereArgs = new String[] { String.valueOf(_id) };
try{
helper.getReadableDatabase().delete("news_table", whereClause,whereArgs);
Cursor cursor = helper.getWritableDatabase().rawQuery("select * from news_table", null);
inflateListView(cursor);
}catch (SQLException e) {
Toast.makeText(getApplicationContext(), "删除数据库失败",
Toast.LENGTH_LONG).show();
return false;
}
return true;
}
//长按listview删除item
OnCreateContextMenuListener listviewLongPress = new OnCreateContextMenuListener() {
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
final AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) menuInfo;
new AlertDialog.Builder(MainActivity.this)
// 弹出窗口的最上头文字
.setTitle("删除当前数据")
//设置弹出窗口的图式
.setIcon(android.R.drawable.ic_dialog_info)
// 设置弹出窗口的信息
.setMessage("确定删除当前记录")
.setPositiveButton("是",
new DialogInterface.OnClickListener() {
public void onClick( DialogInterface dialoginterface, int i) {
// 获取位置索引
int mListPos = info.position;
// 将listview中所有的数据都传入hashmap-listData中
Cursor c = helper.getReadableDatabase().rawQuery("select * from news_table", null);
int columnsSize = c.getColumnCount();
listData = new ArrayList<HashMap<String, Object>>();
while (c.moveToNext()) {
HashMap<String, Object> map = new HashMap<String, Object>();
for (int j = 0; j < columnsSize; j++) {
map.put("_id", c.getString(0));
map.put("news_tittle", c.getString(1));
map.put("news_content", c.getString(2));
}
listData.add(map);
}
HashMap<String, Object> map = listData .get(mListPos);
// 获取id
int id = Integer.valueOf((map.get("_id").toString()));
deleteNews(id);
// 移除数据
}
}
)
.setNegativeButton("否",
new DialogInterface.OnClickListener() {
public void onClick(
DialogInterface dialoginterface, int i) {
// 什么也没做
}
}).show();
}
};
private void queryNews() {
String tittle = et_tittle.getText().toString();
String content = et_content.getText().toString();
Cursor cursor = helper.getReadableDatabase().rawQuery(
"select * from news_table where news_tittle like ? and news_content like ?",
new String[]{"%" + tittle + "%", "%" + content + "%"});
Bundle bundle = new Bundle();
bundle.putSerializable("news", cursor2list(cursor));
Intent intent = new Intent(this, SearchResultActivity.class);
intent.putExtras(bundle);
startActivity(intent);
}
private ArrayList<Map<String, String>> cursor2list(Cursor cursor) {
ArrayList<Map<String, String>> list = new ArrayList<Map<String,String>>();
//遍历Cursor
while(cursor.moveToNext()){
Map<String, String> map = new HashMap<String, String>();
map.put("tittle", cursor.getString(1));
map.put("content", cursor.getString(2));
list.add(map);
}
return list;
}
@Override
protected void onDestroy() {
super.onDestroy();
//释放数据库资源
if(helper !=null)
helper.close();
}
}
新建一个Activity用来显示查询的结果：
package com.example.listview_sqlite_xu;
import java.util.List;
import java.util.Map;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.ListView;
import android.widget.SimpleAdapter;
public class SearchResultActivity extends Activity {
private ListView listView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//设置布局文件
setContentView(R.layout.news_search_result);
//初始化组件
listView = (ListView) findViewById(R.id.lv_search_result);
//获取跳转到该Activity的intent对象
Intent intent = getIntent();
//获取Intent对象所携带的数据
Bundle bundle = intent.getExtras();
//从Bundle中取出List<Map<String,String>>数据
@SuppressWarnings("unchecked")
List<Map<String, String>> list = (List<Map<String, String>>)bundle.getSerializable("news");
SimpleAdapter adapter = new SimpleAdapter(
getApplicationContext(), //上下文对象
list, //数据源
R.layout.item, //List显示布局
new String[]{"tittle", "content"}, //List中map的键值
new int[]{R.id.tittle, R.id.content}); //填充到的布局文件
listView.setAdapter(adapter);
}
}
main_activity的布局文件
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity"
android:orientation="vertical">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="新闻" />
<EditText
android:id="@+id/et_news_tittle"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:singleLine="true"
android:hint="点击此处输入新闻"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="新闻内容" />
<EditText
android:id="@+id/et_news_content"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:lines="2"
android:hint="点击此处输入新闻内容"/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:layout_gravity="center_horizontal">
<Button
android:id="@+id/bt_add"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="onClick"
android:text="添加新闻" />
<Button
android:id="@+id/bt_query"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="onClick"
android:text="查找新闻" />
</LinearLayout>
<ListView
android:id="@+id/lv_news"
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
</LinearLayout>
listview的布局文件：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/tittle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="20dp"
android:textColor="#CC0000"
/>
<TextView
android:id="@+id/content"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="10dp"
android:textColor="#00FF00"/>
</LinearLayout>
查询结果页面布局文件：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ListView
android:id="@+id/lv_search_result"
android:layout_height="wrap_content"
android:layout_width="wrap_content"/>
</LinearLayout>
